The invention relates to a fuel pump having a driven impeller facing a casing part, with rings of guide vanes arranged in the impeller concentrically enclosing one another and defining blade chambers, with partially annular fuel feed ducts facing the rings of guide vanes in the casing part, and with outlet ducts connected to the partially annular ducts, the rings of the blade chambers and the partially annular ducts forming a radially inner delivery chamber and a radially outer delivery chamber. The invention further relates to a fuel feed system for an internal combustion engine of a motor vehicle having such a fuel pump for drawing fuel from a fuel tank and delivering the fuel to the internal combustion engine.
Such fuel pumps are commonly used in fuel feed systems of modern motor vehicles and are known in practice. Here the delivery chambers of the fuel pump serve for filling a swirl pot and for supplying the internal combustion engine of the motor vehicle with fuel. The impeller is generally fixed on a shaft of an electric motor and in normal operation is driven at a rated speed. Particularly when starting the internal combustion engine at low temperatures, however, the rated speed frequently is not reliably achieved, since the electric motor is driven at a low voltage and therefore has only a low power output. This leads, especially in the radially inner delivery chamber, to a greatly reduced delivery capacity of the fuel pump. In the worst case this means that the swirl pot is no longer filled and the delivery of fuel to the internal combustion engine is interrupted.
A further disadvantage of the known fuel feed system is that the impeller in normal operation has to be constantly driven at the rated speed regardless of the fuel demand of the internal combustion engine, in order that the delivery capacity of the radially inner delivery chamber does not fall. This means that the fuel pump has an unnecessarily high energy demand in order to drive the impeller.